Lincoln Electric LF-72/74 service manual 552B + 552A

Page 96

Return to Section TOC

Return to Section TOC

Return to Master TOC

Return to Master TOC

F-12	TROUBLESHOOTING AND REPAIR	F-12
	TROUBLESHOOTING AND REPAIR

DIODE BRIDGE TEST

(continued)

FIGURE F.4 – CONTACTOR

552B

+ 552A -

Return to Section TOC

Return to Master TOC

41

58042

Return to Section TOC

Return to Master TOC

TEST PROCEDURE

1.Remove the input power from the unit.

2.Using a 5/16 nut driver remove the 5 screws holding the cover.

3.Apply the correct input voltage (42VAC) to the LF72/LF74 unit.

4.Check for the correct input voltage at leads 41 and 42 on the bridge. If the input voltage is not there check the wiring back to the receptacle assembly pins I and K.

5.Check for the proper output on leads 580 negative and 522 positive. The voltage should be 59VDC. If you are only reading 38VDC the control circuit is open. Check the wiring and the connections back to your control board.

LF-72/74

Image 96

Contents LF-72/74 Safety Electric Shock can kill Welding Sparks can cause fire or explosion IiiPrécautions DE Sûreté Sûreté Pour Soudage a L’ArcMaster Table of Contents for ALL Sections Table of Contents Installation SectionSection A-1 Installation Amp Rating Duty CycleSafety Precaution LocationMounting Bench Mount Swivel MountBoom Mount SuspendedWeld Cable Sizes Coaxial Weld Cables Weld Cable ConnectionINSTALLATIONA-7 Analog Control CableControl Cable Connections Miller Power Source Lincoln Wire Feeder Analog Miller Control Cable Adapter K2335-1Pin Function Wire Drive Systems Welding GUN/WIRE Feeder Trigger ConnectorRemote Sense Lead Specifications High Frequency ProtectionWelding GUNS, Torches and ACCES- Sories Magnum GUN and Cable AssembliesProcedure for Changing Drive and Idle Roll Sets Wire Drive ConfigurationRolls.FIGURE A.4 Pressure ARM Adjustment Gun Receiver For use With BushingSet the pressure arm as follows See Figure A.6 Wire Reel Loading Weld Wire Routing Figure A.9Shielding GAS Connection Installing Electrode To install Lincoln conduit See Figure A.10bConduit Kits For Codes 11209, 11210, 11211 and aboveAluminum Wire Preparations Figure A.12bINSTALLATIONA-18 Base Model Bench Model Standard Duty Bench Model Heavy DutyTypical System Configurations CableLF-72/74 Operation Section Section B-1Operation GAS Input Work ConnectionCommon Welding Abbreviations Product DescriptionRecommended Processes Front Panel Controls and Connections Figure B.1 Case Front Controls DescriptionBurnback and Postflow Timer KIT Cold FEED/GAS Purge SwitchStep Trigger Interlock Switch Remote Voltage Control KITWire Feed Speed Knob Trigger Connector 5-PIN AmphenolGUN Receiver Bushing K1500-2 Trigger InterlockAccessories Section Section C-1Accessories Optional KitsLF-72s Accessories Key LF-72/74 Maintenance Section Section D-1Maintenance MaintenanceCalibration Specification Routine MaintenanceFigure D.1 Figure D.3 Major Component Location Section AA-1 Section AAWFS Range Wire Sizes AA-2Model AA-3 Figure AA.1AA-4 AA-5 AA-6 Coaxial Weld CableINSTALLATIONAA-7 AA-7K1797-xx AA-8 Drive Roll Kits Steel or Cored Wires AA-9AA-10 Figure AA.3AA-11 Changing the Gun Receiver BushingLation or changing drive rolls and/or GuidesAssembly of Drive Rolls and Wire Guides AA-12AA-13 Set the pressure arm as follows See Figure AA.8AA-14 AA-15 Loading 16 to 44 lb .3 20kg Spools See figure AA.8AA-16 Figure AA.11AA-17 Figure AA.12aAA-18 Figure AA.12bAA-19 AA-20INSTALLATIONAA-20 Common Equipment SET-UPSFigure AA.15 High Volume Production AA-21Figure AA.16 Portable Welding AA-22Section BB-1 Section BBBB-2 Fcaw Innershield or OutershieldRequired Equipment BB-3BB-4 Figure BB.1 Case Front Controls DescriptionBB-5 K2426-1 and K2426-2 modelsK2426-3 model Switch BB-6Section CC-1 CC-2 CC-3 CC-4 CC-5 CC-6 Section DD-1 Section DDTo verify the wire feed speed Nal wiringWhen inching with gun trigger, electrode WFS knob setting Could remain energized Several secondsMAINTENANCEDD-3 DD-3Figure DD.3 Major Component Location DD-4Theory of Operation Section Section E-1Theory of Operation Return to SectionControl Board LF-72/74 Troubleshooting & Repair Section Section F-1Troubleshooting & Repair HOW to USE Troubleshooting GuidePC Board Troubleshooting Procedures Function Problems Function Problems Troubleshooting & Repair Drive Motor and Tach Feedback Test Test DescriptionTest Procedure Troubleshooting and Repair GAS Solenoid TestTest Procedure Figure F.3 Leads 552, 552BDiode Bridge Test 552B + 552A Wire Speed Potentiometer Test Wire Speed Potentiometer Test 14F-14PC Board Removal and Replacement Control PC Board Removal and Replacement Procedure Removal Procedure Replacement ProcedureTroubleshooting and Repair Wire Drive Motor and Gear BOX Removal and Replacement ProcedureProcedure Replacement Procedures SET UP Operation VerificationLF-72/74 Electrical Diagrams Section Section G-1Electrical Diagrams LF-72/74Timer KIT Board Normal Speed Micro Internal panel Motor Connecter Summary High Torque Setting engages Schematic Common Analog Control PC Board G4559 Sheet Electrical Diagrams Electrical Diagrams PC Board Assembly Common Analog Control G4560-2E0